It hasn’t been an easy summer for the beverage industry in the Big Apple. In May, New York City Mayor Michael Bloombergproposed a ban on over-sized sodas in the city, and now New York attorney general Eric T. Schneiderman, is probing energy drink makers over whether or not they deceived customers about their product ingredients and health risks.

A recent Wall Street Journal article reports that In July, Schneiderman subpoenaed large energy drink makers Monster Beverage, PepsiCo and Living Essentials. Monster produces Monster Energy Drinks, PepsiCo makes AMP drinks and Living Essentials makes 5-Hour Energy, all popular energy boosters that are widely advertised, particularly among younger audiences. The subpoenas are part of an investigation into whether the companies have accurately disclosed how much caffeine their drinks contain and if they violated federal laws by marketing their products as supplements instead of foods, which are more strictly regulated.

A state official told the New York Times anonymously that there is concern the manufacturers do not disclose all their ingredients. Additives like black tea extract could add to the beverages’ caffeine levels, but aren’t included on the products’ label. Other caffeine-laden ingredients, like guarana, may be listed but consumers aren’t made aware that they are another source of caffeine.

Energy drinks have become a multimillion dollar industry with U.S. sales increasing 16% last year to $8.9 billion, according to the Wall Street Journal. This accounts for 12% of the carbonated-soft-drink category.

The amount of caffeine in beverages can range from about 80 milligrams to more than 500 milligrams, and the health risks of too much caffeine consumption include cardiovascular problems. Health officials are also concerned about the common practice among young consumers of mixing energy drinks and alcohol, since the stimulation from the caffeinated energy drinks can mask intoxication.

The New York Times article cites a recent report on teen caffeine use:

A November 2011 report by the Drug Abuse Warning Network, produced under the auspices of the Department of Health and Human Services, showed a tenfold increase in emergency room visits linked to energy drinks from 2005 to 2008.

“Consumption of energy drinks is a rising public health problem because medical and behavioral consequences can result from excessive caffeine intake,” the report concluded. “A growing body of scientific evidence documents harmful effects, particularly for children, adolescents and young adults.”

In a statement, the American Beverage Association declined to comment on the investigation, but says consumers can be confident that ingredients and labels in energy drinks are regulated by the U.S. Food and Drug Administration. “Despite the misperception, most mainstream energy drinks contain about half the caffeine of a similar size cup of coffeehouse coffee. And, the caffeine content our members voluntarily display on their packages reflects total caffeine amounts, including those that come from other sources, such as additives,” they write.

If the investigation shows that the companies violated federal law in misleading consumers, they could be charged civil fines and be forced to changed their labeling.